The present inventors have focused on the effects of a s-triazine [1,3,5-triazine] derivative and a pyrimidine derivative substituted with a benzimidazole ring against solid tumors, and have performed research on the synthesis of numerous compounds and the relationship between anti-tumor activities and chemical structures (Patent Documents 1, 2, 3, 4 and 5).
As a result of this research, the present inventors found that a s-triazine derivative and a pyrimidine derivative having a specific substituent at position 2 of the benzimidazole ring such as, for example, 2-(2-difluoromethylbenzimidazol)-4,6-dimorpholino-1,3,5-triazine and others, have an especially strong effect against solid tumors and are effective as anti-tumor agents (Patent Documents 3, 4 and 5).
Furthermore, the present inventors found that these s-triazine and pyrimidine derivatives have an immunosuppressive effect and are effective against disorders that respond to immunosuppressants, such as autoimmune diseases, organ transplantations, allergic diseases, hematological tumors and sepsis (Patent Document 6).
The present inventors have continued to perform research on improvements in order to further increase the efficacy of these heterocyclic compounds (s-triazine and pyrimidine derivatives) as therapeutic agents for various diseases.    Patent Document 1: WO 99/05138    Patent Document 2: WO 00/43385    Patent Document 3: WO 02/088112    Patent Document 4: WO 2004/037812    Patent Document 5: WO 2005/095389    Patent Document 6: WO 2006/095906